Robotic transport apparatus

ABSTRACT

A robotic transport apparatus is capable of providing an effective waterproofing function of working components without using mechanical seals. The robotic transport apparatus includes a robot body, an arm assembly extendably attached to the robot body, and a workpiece holding section attached to the arm assembly. A pan member for waterproofing of the robot body is provided between the workpiece holding section and the robot body and has an area not smaller than the workpiece holding section.

This is a divisional application of Ser. No. 08/808,690, filed Feb. 28,1997, now U.S. Pat. No. 5,893,794.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a robotic transport apparatus suitablefor transporting workpieces in a semiconductor device manufacturingsystem, for example, including wet and/or dirty processes such as a CMP(chemical mechanical polishing) system.

2. Description of the Related Art

In a semiconductor wafer manufacturing process, a polishing apparatus iscommonly used to provide a flat mirror polished surface on wafers. Sucha polishing apparatus comprises a turntable and a top ring independentlyrotated relative to each other, and a wafer held on the underside of thetop ring is polished by pressing the wafer against a polishing surfaceprovided at the top surface of the turntable while supplying an abrasiveliquid onto the surface. The polishing apparatus also includes a waferstorage unit for placing a cassette including wafers to be polished, acleaning unit for cleaning and drying the polished wafers, and atransport apparatus for transporting the wafers between the processingunits.

An example of such transport apparatus is shown in FIG. 11. Theapparatus comprises a cylindrical robot body 10 and a set of arm devices21 disposed on the top surface of the robot body 10. Each arm device 21comprises two arms 25, 27 having articulating joint sections 35, 37, andthe upper arm 27 is provided with a hand member (workpiece holdingsection) 41 disposed at the tip end of a connection member 33 through anarticulating joint section 38.

An example of the configuration of the hand member is shown in FIG. 12.The hand member 41 is substantially plate-shape and has a recess in itscentral region serving as a receiving section 81 which is surroundedwith protruding guides 83. The receiving section 81 comprises a wafercontact surface 85 for abutting the lower surface edges of a wafer W,and a bottom section surface 87 which is disposed inwardly of the wafercontact surface 85 at a lower level than the wafer contact surface 85.On the other hand, a top ring 90 is of a circular shape, and is providedwith a bottom vacuum suction surface 91 and a guide ring 97 attached toits periphery.

To transfer the wafer W from the top ring 90 to the hand member 41 ofsuch an arrangement, the hand member 41 is placed directly below the topring 90 holding the wafer W by vacuum suction, and then the vacuum holdon the wafer is released by shutting off the vacuum suction so that thewafer W will drop into the receiving section 81 of the hand member 41.This operation is illustrated by designating the hand member 41 withsingle dot lines in the top portion of FIG. 12. After dropping the 25wafer W, the hand member 41 is moved away downwardly.

This type of robotic transport apparatus is used to transport the wafersW to various processing apparatuses for various processing steps, suchas polishing and cleaning steps, by means of the connection member 33.The wafers are often dripping with processing liquid, and intransporting wet wafers liquid droplets falling from the wafers of tenaccumulate on the top surface of the robot body 10.

When the quantity of liquid droplets increases to fill the gapsurrounding the articulating joint section 35, as illustrated by shadedareas 39 in FIG. 11, the liquid can penetrate into the arm 25 and robotbody 10 through crevices in the joint section 35. Such seepage of liquidleads to corrosion of the mechanisms to generate malfunctioning of theworking parts, leading to increased requirements for maintenance. Suchoperational problems lower the cost performance ratio of the apparatusand lead to loss of productivity. The same problems occur when theliquid seeps into joint sections 37, 38.

To prevent such seepage of liquid, a usual practice is to use mechanicalseals, however, such contact seals have still some clearance and are nottotally water tight, and it has been extremely difficult to prevent suchliquid seepage into critical operating components of the apparatus.Furthermore, when 0-rings, which are known to provide effective contactsealing, are used to seal joint section 35, 37 or 38, although theseepage clearance is reduced by the strong elastic sealing force of theO-rings, the local frictional forces are increased owing to the largefrictional forces exerted by the compressed O-rings. The result is adrop in the operational speed of the arms 25, 27. On the other hand, ifthe speed of the arms 25, 27 is to be maintained, it is necessary toprovide a larger torque for arm rotation, thus generating a problem ofneed for a driving motor with a larger driving capacity.

Also, the conventional design of the guide member 83 is such that theupper edge thereof is formed at right angles to the vertical, and ifthere is a misalignment between the top ring 90 and the hand member 41,the outer periphery of the wafer W can easily become lodged in theangular section of the guide member 83, thus preventing the wafer W frombeing safely deposited within the receiving section 81.

Another problem with the existing design of the robotic transportapparatus for handling the wafers is that the bottom section surface 87of the hand member 41 often becomes contaminated with droplets 99 ofliquid from sources such as abrasive liquid. Droplets 99 form spheresdue to the surface tension on the bottom section surface 87 asillustrated in FIG. 12, and the diameter of such a sphere may exceed theseparation distance between the wafer contact surface 85 and the bottomsection surface 87 which commonly is only about 1.5 mm. Therefore, thedroplet 99 could easily grow to contact the surface of the wafer W. Itcan be seen that if a hand member 41, having such large droplets 99 ofabrasive liquid, is used to pickup a wafer W from a cleaning device, itcan lead to a problem that the cleaned wafer has now become contaminatedwith the substances in the abrasive liquid.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a robotictransport apparatus which can provide an effective waterproofingfunction for working components without using mechanical seals.

It is another object of the present invention to provide a robotictransport apparatus which can safely receive workpieces into a receivingsection of a hand member to assure stable transportation of theworkpieces, eliminate the possibility of contaminating the workpieces byliquid located at the hand member, and also lighten the weight of thehand member.

These objects are achieved by providing a robotic transport apparatusincluding a robot body, an arm assembly extendably attached to an uppersurface of the robot body, a workplace holding section attached to thearm assembly, and a pan member for waterproofing having a projectionarea not smaller than the workplace holding section, provided betweenthe workplace holding section and the robot body.

Accordingly, transfer of liquid from the workplaces to the robot bodyand seepage of liquid into joint sections of the arm assembly isprevented, to thus provide stable operation and a long service life ofthe system.

In another aspect of the transport apparatus, the arm assembly may beprovided with a connection member connected to the workplace holdingsection in a manner to bypass the pan member. The pan member may beprovided with a drainage pipe to remove waste liquid. The transportapparatus may be provided with a driving mechanism to enable the deviceto move along a transport path, and a trench may be provided alongsidethe transport path so that the waste liquid may be removed therethrough.

In another aspect of the invention, a transport apparatus includes arobot body, an arm assembly extendably attached to an upper surface ofthe robot body, and a workpiece holding section attached to the armassembly, the workpiece holding section having a receiving section ofrecessed configuration for receiving a workpiece, and the receivingsection including a contact surface for contacting lower peripheralsurfaces of the workpiece and a bottom section surface disposed on aninner side of and at a lower level than the contact surface. Aseparation distance between the contact surface and the bottom sectionsurface is selected to be not less than a maximum diameter of a dropletformed by a liquid that can be present at the bottom section surface.The separation distance should be greater than 3 mm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall plan view of an embodiment of a polishing apparatusof the present invention.

FIG. 2 is a perspective view of the flow of processed wafers beingtransported by a robotic transport apparatus of the present invention.

FIG. 3 is a cross-sectional view of the robotic transport apparatus ofthe present invention.

FIG. 4 is a perspective view of the robotic transport apparatus of thepresent invention.

FIG. 5 is a perspective view of a hand member.

FIG. 6 is a cross-sectional view of the hand member taken along a planeVI--VI in FIG. 5.

FIG. 7 is a cross-sectional view of a bottom section of anotherembodiment of the hand member of the present invention that would besimilar to that taken along plane VII--VII in FIG. 5.

FIG. 8 is a perspective view of another embodiment of the hand member.

FIG. 9 is a schematic perspective view of the chuck mechanism and thehand member.

FIG. 10 is a perspective view showing the robotic transport apparatushaving a hand member and a waterproof pan member.

FIG. 11 is a schematic side view of a conventional robotic transportapparatus.

FIG. 12 is an illustration of the process of transfer of a wafer betweena top ring and a hand member in the conventional robotic transportapparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, preferred embodiments will be explained with referenceto the drawings.

As shown in FIGS. 1 and 2, the polishing apparatus comprises a polishingsection 100, a cleaning section 200, a storage section 300 for storingwafers W, and a transport apparatus 400 having two robotic transportapparatuses 402, 404 for transporting wafers W.

The polishing section 100 comprises a turntable 102 having a polishingsurface 103, a polishing unit 106 having a top ring 104, a dressing unit110 having a dressing tool 108, and a workpiece delivery device orhandling unit 112.

The cleaning section 200 comprises primary and secondary cleaningdevices 202, 204 and spin dryers (which may have washing capability) 206disposed in a side-by-side arrangement on one side of the centrallydisposed transport apparatus 400, and a wet workpiece turning device 208and a dry workpiece turning device 210 disposed in a side-by-sidearrangement on the other side of the transport apparatus 400.

FIG. 2 shows a perspective view of essential parts of the transportapparatus 400 and the cleaning section 200. As shown in the drawing,robotic transport apparatuses 402, 404 are each provided with two setsof arm assemblies 21. At the tip of each arm assembly 21 are providedrespective hand members (workpiece holding sections) 502, 503 and 504,505 for holding wafers W. The hand members 502, 503 and 504, 505 arearranged so that top hand member 502 superimposes bottom hand member 503and likewise for the other set of top and bottom hand members 504, 505.

As shown in FIG. 3, a cross-sectional view of the robotic transportapparatuses 402, 404, each of the arm assemblies 21 comprises two arms25, 27 respectively connected to robot body 10 and together byarticulating joint sections 35, 37. Substantially U-shaped connectionmembers 33a, 33b are joined to the arms 27 by articulating jointsections 38, and plate-shaped hand members 502 (504), 503 (505) forholding the wafers W are provided at tips of respective of theconnection members 33a, 33b. Therefore, the hand members 502 (504), 503(505) are connected to the arms 27 in a manner to bypass or bepositioned outwardly of a waterproof pan member 50 which will bedescribed hereinafter. That is, each of the hand members 502 (504), 503(505) is generally aligned vertically above the tip of the respectivearm 27 and the respective articulating joint section 38. The handmembers 503 (505), 502 (504) are provided at the tips of the respectiveconnection members 33a, 33b so that they superimpose vertically withouttouching each other. Each of the hand members 503 (505), 502 (504) iscapable of holding on an upper surface thereof a wafer W.

In this embodiment, the connection member 33b is disposed below theconnection member 33a, and waterproof pan member 50 or liquid reservoiris provided between the articulating joint sections 38 and the handmember 503 (505) attached to the lower connection member 33b. The sizeof the waterproof pan member 50 is chosen so that length and widthdimensions thereof are larger than the diameter of the wafer W which isbeing held in the connection members 33a, 33b. Thus, a projection in ahorizontal plane of the waterproof pan member 50 covers that of the handmember 503 (505). In this embodiment in particular, the length and widthdimensions of the pan member 50 are larger than the diameter of robotbody 10, and are larger than the hand members which serve as theworkpiece holding sections. Also, the waterproof pan member 50 extendsorthogonally at right angles to transport direction Z (FIG. 4). In otherwords, the waterproof pan member 50 is disposed so as to guard theentire area of movement of wafers W above the robot body 10.

As shown in FIGS. 3 and 4, a drainage pipe 51 is connected to a certainlocation of the waterproof pan member 50, and the bottom end of thedrainage pipe 51 is inserted into a second waterproof pan member 53 of aring shape arranged about the outer periphery of the robot body 10. Thepan member 50 should be disposed at an incline to tilt towards thelocation of attachment of the drainage pipe 51 so as to facilitatedraining. The second pan member 53 is also provided with a drainage pipe55 whose bottom end is inserted into a trench 57. The robotic transportapparatuses 402, 404 are constructed so that they can move towardsvarious processing locations, such as the polishing section 100 and thecleaning section 200, by proceeding in the direction Z shown in FIG. 4.The trench 57 is formed, as shown in FIG. 4, along one side of the tworobotic transport apparatuses 402, 404 over the entire length ofmovement thereof. The trench 57 is also provided with a drainage pipe59. A third waterproof pan member 61 is provided on the left side of therobotic transport apparatus (as viewed in FIG. 4 and omitted in FIG. 3),and a drainage pipe 62 provided on the third pan member 61 is insertedinto the trench 57. Opposite to the trench 57, a fourth waterproof panmember 63 is provided over the entire length of movement of the robotictransport apparatus. A fifth waterproof pan member 65 is provided belowthe robot body 10, as shown in FIG. 3 and omitted in FIG. 4.

The hand member 502 has a vacuum suction mechanism to hold wafers Wthereon and is used to handle only dry wafers W, while all the otherhand members 503, 504 and 505 (all represented by 503 hereinbelow) arefor handling wet wafers W wetted by liquids such as polishing, rinsingor cleaning liquids. The wet workpiece hand members 503 have a shelfshaped tray for receiving the workpiece at the periphery thereof. Asshown in FIG. 5, the hand member 503 is constructed to include areceiving section 511 of a depressed shape for storing circular shapedwafers W and formed in the center region of the hand member 503, outerguide portions 531 on opposite sides of the receiving section 511, and ahandle portion 551 protruding from one outer guide position 531.

The receiving section 511 includes two arc shaped contact surf aces 513for abutting the outer periphery of the wafer W, bottom section surfaces515 at a lower level than the contact surfaces 513 and disposed betweenthe two contact surfaces 513, and a drainage opening 517 disposedcentrally between bottom section surfaces 515. All regions of the bottomsection surfaces 515 are inclined to slope towards the drainage opening517 to serve as tapered drainage surfaces P for liquid drainage. Aheight difference T1 (FIG. 6) between the contact surfaces 513 and thehighest position of the bottom section surfaces 515 is larger than themaximum dimension of a liquid droplet grown by surface tension effectsand located on a bottom section surface 515. In this embodiment, theheight dimension T1 is chosen to be larger than 6 mm. On the other hand,the upper inside edge of each guide portion 531 has a tapered guidesurface 533 inclined outwardly and upwardly. The taper angle θ of theguide surface 533 should not be too large for the wafer W to slide downalong the guide surface 533, so a preferred angle is about 20 degrees.

To prevent corrosion on the hand member 503 or metallic contamination ofthe wafer W, the hand member 503 made of a metal plate (for example,aluminum or SUS plate) coated with a polymeric coating material. Insteadof a polymeric coating, it is also permissible to attach polymer partsprepared separately to the hand member 503 for constructing the regionsof direct contact with wafer W, i.e., the inside surfaces including theguide surfaces 533 of the guide portions 531 and the contact surfaces513. The handle portion 551 is attached to the tip of the respectiveconnection member 33a, 33b.

The overall operation of the polishing apparatus will be explained withreference to FIGS. 1 and 2. The hand members 502 to 505 of the robotictransport apparatuses 402, 404 are independently extendable inhorizontal and vertical directions. When cassette 302 containingpre-polishing wafers W is placed in the location shown in the drawings,the hand member 502 of the robotic transport apparatus 402 removes onewafer W at a time from the cassette 302 and transfers it to theworkpiece turning device 210 which turns over the wafer W. From theturning device 210, the wafer W is passed onto the hand member 504 ofthe transport apparatus 404, and is transported to the workpiecedelivery device 112 of the polishing section 100. The wafer W on theworkpiece delivery device 112 is transferred onto the bottom surface ofthe top ring 104 of the polishing unit 106 (which swings in thedirection of the arrow R₁, shown in FIG. 1) and is positioned on theturntable 102, and is polished by the rotating polishing surface 103.The polishing surface 103 is supplied with an abrasive liquid through asupply pipe (not shown) during the polishing operation. The polishedwafer w is again returned to the workplace delivery device 112, and istransferred to the workplace turning device 208 by the hand member 505of the robotic transport apparatus 404 and is turned over while beingrinsed with a rinsing liquid. The wafer W is then transported to theprimary cleaning device 202 by the hand member 505 to be cleaned, thenonto the secondary cleaning device 204 by the hand member 504 to becleaned, and is transported to the spin dryer 206 by the hand member 503to be dried therein, and is returned to the original cassette 302 by thehand member 502. The dressing unit 110 shown in FIG. 1 is used to dressthe polishing surface 103 by moving onto the turntable in the directionof arrow R₂ and by pressing the dressing tool 108 onto the rotatingpolishing surface 103.

In this arrangement of the polishing apparatus, the hand member 502 isforkshaped and is used only to handle dried wafers W, and all otherwafers W wet with polishing, rinsing or cleaning liquid are handled bythe hand members 503-505, each of which has a drip tray. Thisarrangement prevents the wafers W from being contaminated through theuse of the hand members 502-505.

In the above steps, when the wafers W are handled by the hand members503-505 in the polishing section 100 or in the cleaning section 200, theliquid from the wet wafers W will drip down, but the robot body 10 iscompletely protected from becoming wet by the first waterproof panmember 50, thus preventing droplets from falling onto the upper surfacesof the robot body 10 and the arms 25, 27. Therefore, there is no dangerof liquid seeping from the articulating joint sections 35, 37 and 38into the arms 25, 27 or into the robot body 10. The liquid dropletsfalling onto the pan member 50 are 25 collected in the trench 57 afterpassing through the drainage pipe 51, the second waterproof pan member53, and the drainage pipe 55 and are discarded externally through thedrainage pipe 59. The second pan member 53 not only performs thefunction of guiding the liquid droplets falling on the pan member 50 tothe trench 57, but also performs the function of collecting the dropletseven when the droplets which should have fallen into the pan member 50are accidentally scattered about the robot body 10 by some event such asvibration, for example. When handling the wafers W in the polishingsection 100 or in the cleaning section 200, the wafers W extendoutwardly of the pan member 50, but the droplets which fall from thewafers W are collected in the third and fourth pan members 61, 63 and inthe trench 57, and are drained through the drainage pipe 59 and thefifth pan member 65 (FIG. 3).

It will be apparent from the above that the first and second pan members50 and 53 primarily serve the purpose of preventing droplets fromfalling onto the workpiece transport apparatuses, and the third, fourthand fifth pan members 61, 63 and 65 primarily serve the purpose ofpreventing the droplets from falling onto facilities and devices whilethe wafers W are being handled between the wafer transport apparatusesand wafer processing devices. Water removal means such as trench 57 areused commonly for both purposes. Each pan or trench may be formed tohave a tapered cross section widening towards an upper opening tofacilitate fluid inflow.

Next, the role of the hand members 503-505 will be explained further.When the wafer W held by the top ring 90 shown in FIG. 12, for example,is to be dropped into the hand member 505, the hand member 505 isbrought directly below and adjacent to the top ring 90 holding the waferW. The vacuum on the top ring 90 is then released so that the wafer Wmay be dropped into the receiving section 511 of the hand member 505.When the wafer W is dropped, even if the top ring 90 and the hand member505 happen to be misaligned, the wafer W can slide down safely into thereceiving section 511, by having the outer periphery of the wafer Wguided by the guide surfaces 533 provided on the guide portions 531,without a danger of the wafer W being stuck at the upper edge of theguide portions 531. It can be understood that the droplets from theabrasive liquid and water used in polishing the wafer W adhere to thetop ring 90, and they may easily fall onto the hand member 505 andcollect on its upper surface. However, as illustrated in FIG. 6, thehand member 505 is designed so that even when the largest droplet 540 isformed, the clearance provided by the separation distance T1 between thebottom section surfaces 515 and the contact surfaces 513 is greater thanthe height dimension of the droplet 540, and there is no danger of thedroplet 540 touching the bottom region of a wafer W. It should furtherbe noted that because the bottom section surfaces 515 serve as tapereddrainage surfaces P for liquid removal, the droplets 540 attached to thebottom section surfaces 515 slide along the tapered surfaces P and areremoved by falling through the drainage opening 517. Furthermore,because of the presence of the drainage opening 517, the area of thebottom section surfaces 515 for receiving the droplets falling from thetop ring 90 and wafers W becomes small, and little liquid will remain onthe bottom section surfaces 515. Even if the droplets 540 should grow toa large size, there is no danger of the wafer W touching the droplets540, thus totally preventing contamination of the wafer W by potentiallyharmful liquid. Further, since the hand member 505 is provided with thedrainage opening 517, the weight of the hand member is reduced. Thedroplets dripping from the opening 517 or from around the periphery ofthe hand member 505 run into the waterproof pans 50, 53.

It is clear that the beneficial effects of the design and arrangement ofthe hand members in transferring the wafers W from the top ring applyequally in the case of transferring the wafers W or handling wafers W inother devices, such as the wafer turning devices and spin dryers.

FIG. 7 is a cross-sectional view of another embodiment of the handmember, which corresponds to a view that would be through plane VII-VIIshown in FIG. 5. As shown in FIG. 7, bottom section surface 515acomprises a central high region and tapered drainage surfaces P forremoving liquid. This configuration provides the same advantages asthose described in the previous embodiment. It is obvious that the shapeof the receiving section, tapered drainage surface P and openingspresented in the previous embodiment are only illustrative examples, andthey can be designed in many different ways to achieve the same purpose.

FIGS. 8 to 10 are perspective views of another embodiment of a handmember 503a of the present invention. The parts of this hand member 503awhich are the same as or similar to those of the hand member 503 shownin FIG. 5 are given the same reference numerals, and their detailedexplanations will be omitted. The differences between the hand membersshown in FIG. 5 and FIG. 8 are that the receiving section 511 of thehand member 503a has a longitudinal cut-out 560, and a protrusionsection 561 is formed on the upper surface of the handle portion 551.The presence of the cut-out 560 causes the drainage opening 517 to besplit into two sections, and each of the openings 517 is provided with atapered drainage surface P.

With the hand member of FIG. 8, in addition to the benefits associatedwith the hand member shown in FIG. 5, the following advantages areobtained. The cut-out 560 reduces the area of the contact surfaces 513,thereby reducing the area of contact of the surfaces 513 with the waferW, thereby further reducing the sites of potential contamination sourcessuch as dust particles. Another advantage is that the presence of thecut-out 560 facilitates transferring of the wafer W to and from a waferrotation device having a clamp mechanism for holding the wafer W. Forexample, the secondary cleaning device 204 and the spin dryer 206 shownin FIG. 1 require the wafer W to be held and rotated in a clamp suchshown in FIG. 9. Such an operation can be performed by clamping theouter periphery of the wafer W with concentric hooks 71 shown in FIG. 9so that the wafer W may be rotated. This configuration of the handmember 503a enables it to be placed under the clamped wafer W bylocating a hook or hooks 71 within the cut-out 560 of the hand member503a while the wafer W is being clamped by the set of hooks 71.

The protrusion section 561 on the handle portion 551 serves as a splashguard to prevent liquid droplets splashing from a wafer W from reachingthe robot body while the hand member 503a is handling the wafer W. Inthis embodiment, because of the presence of the pan member 50 providedbelow the hand member 503a attached to the arm assembly 21 of thetransport apparatus 402, there is no danger of the robot body becomingwet even if droplets fall from the hand member 503a.

It should also be noted that although a plurality of hand members502-505 are provided on each of the two transport apparatuses 402, 404,the number of hand members is chosen for each application, and only onehand member may be sufficient in some cases. It will be equally clearthat the number, attachment position and shape of the waterproof panmembers are not limited by the examples shown in the illustratedembodiments. Although the waterproof pans are fixed relative to therobot body in the illustrated embodiments, one or more of the pans maybe constructed movable to correspond with movement of a member.Flexibility is permitted within the scope of the invention to achievesplash protection for the robot body and articulating joints and othercritical components of the robotic transport apparatus.

It should be noted also that although the operation of the hand memberis disclosed herein in association with a polishing application, it isobvious that the transport apparatus of the present invention can begenerally employed equally to other semiconductor processingapplications, including photolithography, other types of cleaningfacilities and sputtering equipment.

What is claimed is:
 1. A robotic transport apparatus for transporting aworkpiece, said apparatus comprising a robot body and a workpieceholding section connected to said robot body, said workpiece holdingsection including a receiving section of recessed configuration forreceiving a workpiece, said receiving section comprising:a contactsurface for contacting a lower peripheral surface of the workpiece; anda bottom section surface positioned inwardly of said contact surface andlocated at a level at least 3 mm below said contact surface.
 2. Arobotic transport apparatus for transporting a workpiece, said apparatuscomprising a robot body and a workpiece holding section connected tosaid robot body, said workpiece holding section including a receivingsection of recessed configuration for receiving a workpiece, saidreceiving section comprising:a contact surface to for contacting a lowerperipheral surface of the workpiece; and a bottom section surfacepositioned inwardly of said contact surface and located at a level belowsaid contact surface, said bottom section surface having formed thereina drainage opening.
 3. A workpiece holding section to be employed as apart of a robotic transport apparatus for transporting a workpiece, saidworkpiece holding section including a receiving section of recessedconfiguration for receiving a workpiece, said receiving sectioncomprising:a contact surface for contacting a lower peripheral surfaceof the workpiece; and a bottom section surface positioned inwardly ofsaid contact surface and located at a level at least 3 mm below saidcontact surface.
 4. A workpiece holding section as claimed in claim 3,wherein said level of said bottom section surface is at least 6 mm belowsaid contact surface.
 5. A workpiece holding section as claimed in claim3, wherein said bottom section surface has therein a drainage opening.6. A workpiece holding section as claimed in claim 5, wherein saidbottom section surface is inclined downwardly toward said opening.
 7. Aworkpiece holding section as claimed in claim 5, wherein said contactsurface includes two spaced contact surface portions on opposite sidesof said opening.
 8. A workpiece holding section as claimed in claim 3,wherein said bottom section surface is inclined downwardly.
 9. Aworkpiece holding section as claimed in claim 3, wherein said bottomsection surface includes a central high region and surface portions onopposite sides of said central high region that incline downwardly inopposite directions therefrom.
 10. A workpiece holding section asclaimed in claim 3, wherein said receiving section is divided into twospaced receiving section portions by a longitudinal cut-out.
 11. Aworkpiece holding section as claimed in claim 10, wherein each saidreceiving section portion includes a respective contact surface portionand a respective bottom section surface portion.
 12. A workpiece holdingsection as claimed in claim 11, wherein each said bottom section surfaceportion has therein a drainage opening.
 13. A workpiece holding sectionas claimed in claim 3, further including a guide portion positionedoutwardly of said receiving section, said guide portion having a taperedsurface positioned at a level above said contact surface.
 14. Aworkpiece holding section as claimed in claim 3, including a handlehaving an upper surface having extending therefrom a protrusion.
 15. Aworkpiece holding section to be employed as a part of a robotictransport apparatus for transporting a workpiece, said workpiece holdingsection including a receiving section of recessed configuration forreceiving a workpiece, said receiving section comprising:a contactsurface for contacting a lower peripheral surface of the workpiece; anda bottom section surface positioned inwardly of said contact surface andlocated at a level below said contact surface, said bottom sectionsurface having formed therein a drainage opening.
 16. A workpieceholding section as claimed in claim 15, wherein said bottom sectionsurface is inclined downwardly toward said opening.
 17. A workpieceholding section as claimed in claim 15, wherein said contact surfaceincludes two spaced contact surface portions on opposite sides of saidopening.
 18. A workpiece holding section as claimed in claim 15, whereinsaid bottom section surface includes a central high region and surfaceportions on opposite sides of said central high region that inclinedownwardly in opposite directions therefrom.
 19. A workpiece holdingsection as claimed in claim 15, divided into two spaced receivingsection portions by a longitudinal cut-out.
 20. A workpiece receivingsection as claimed in claim 19, wherein each said receiving sectionportion includes a respective contact surface portion and a respectivebottom section surface portion.
 21. A workpiece receiving section asclaimed in claim 20, wherein each said bottom section surface portionhas therein a respective said drainage opening.
 22. A workpiecereceiving section as claimed in claim 15, further including a guideportion positioned outwardly of said receiving section, said guideportion having a tapered surface positioned at a level above saidcontact surface.
 23. A workpiece holding section as claimed in claim 15,including a handle having an upper surface having extending therefrom aprotrusion.
 24. A polishing apparatus comprising:a polishing table; aworkpiece holder for holding and pressing a workpiece against apolishing surface of said polishing table while supplying an abrasiveliquid; a workpiece storage unit for storing workpieces to be polished;and a transport mechanism for transporting the workpieces between saidworkpiece storage unit and said workpiece holder, said transportmechanism comprising a robotic transport apparatus including a robotbody and a workpiece holding section connected to said robot body, saidworkpiece holding section including a receiving section of recessedconfiguration for receiving a workpiece, said receiving sectioncomprising:a contact surface to contact a lower peripheral surface ofthe workpiece; and a bottom section surface positioned inwardly of saidcontact surface and located at a level at least 3 mm below said contactsurface.
 25. A polishing apparatus comprising:a polishing table; aworkpiece holder for holding and pressing a workpiece against apolishing surface of said polishing table while supplying an abrasiveliquid; a workpiece storage unit for storing workpieces to be polished;and a transport mechanism for transporting the workpieces between saidworkpiece storage unit and said workpiece holder, said transportmechanism comprising a robotic transport apparatus including a robotbody and a workpiece holding section connected to said robot body, saidworkpiece holding section including a receiving section of recessedconfiguration for receiving a workpiece, said receiving sectioncomprising;a contact surface to contact a lower peripheral surface ofthe workpiece; and a bottom section surface positioned inwardly of saidcontact surface and located at a level below said contact surface, saidbottom section surface having formed therein a drainage opening.